The proposed research concerns interactions between DNA and the proteins involved in the replication and morphogenesis of filamentous bacteriophages, and the proteins regulating structure and function in eukaryotic chromosomes. To be sought is knowledge of the structures of multisubunit-protein-DNA complexes, with emphasis on the chemical groups critically involved in binding, and knowledge of the kinetics and thermodynamics of the formation of such complexes. The methods will be analytical centrifugation, ultraviolet absorption and circular dichroism, light scattering, chemical modification, and electron microscopy. The results are to be interpreted in relation to virus replication and assembly, and, in the case of DNA-histone interactions, to mechanisms of gene regulation in the eukaryotic cells. The research also concerns the behavior of macromolecules in solution. The size, shape, and solution dynamics of proteins, nucleic acids, and nucleoproteins will be studied by various physical techniques. To be sought is knowledge of the effects of pH, ionic strength, temperature, and, especially, protein binding on their solution properties. BIBLIOGRAPHIC REFERENCES: Berkowitz, S.A. and Day, L.A. (1976). Mass, length, composition, and structure of the filamentous bacterial virus fd. J. Mol. Biol. 102, in press. Wiseman, R.L., Berkowitz, S.A. and Day, L.A. (1976) Different arrangements of protein subunits and single stranded circular DNA in the filamentous bacterial viruses fd and Pfl. J. Mol. Biol. 102, in press.